Magnetically enhanced inductively coupled plasma etching of 6H-SiC

In this study, 6H-SiC wafers were etched using a magnetically enhanced inductively coupled SF₆-based plasmas (MEICP) and their etch characteristics were investigated. The etch characteristics of SiC and the etch selectivities over metal thin films such as Cu and Ni were investigated as a function of inductive power, operating pressure, additive gas percentage, etc. To understand the etch mechanism, the etched SiC and Cu surfaces were examined by X-ray photoelectron spectroscopy (XPS) and the radical and ion densities in the plasmas were measured by optical emission spectroscopy (OES) and a Langmuir probe, respectively. The obtained highest etch rate was about 1.9 μm/min with 90%SF₆/10%O₂. By XPS analysis, it could be confirmed that the addition of small oxygen percentage assisted in forming volatile SiFx by the reaction with carbon on the SiC surface. In our experimental conditions, the increase of thickness by the formation of a reaction product instead of etching was observed on the Cu mask layer, therefore, the calculated selectivity of SiC to Cu was infinite. Using the Cu mask, 80-100 μm thick SiC substrates could be fully etched with vertical etch profiles and smooth etch sidewalls.